Image and video processing apparatuses and methods

An image processing apparatus for compressing or decompressing a segment of an image, the segment comprising a plurality of pixels, each pixel comprising a pixel value and a pixel position defined by a first coordinate system, the pixel values of the plurality of pixels forming a pixel value vector, the apparatus comprising:

• processing circuitry configured to compress and/or decompress the segment of the image,
• wherein the processing circuitry is configured to, in compressing the segment, compute a plurality of expansion coefficients by expanding the pixel value vector into a plurality of basis vectors, the basis vectors being discrete approximations of solutions of a boundary value problem of the Helmholtz equation on the segment of the image in a second coordinate system, the second coordinate system being rotated relative to the first coordinate system by a rotation angle;
• and/or
• wherein the processing circuitry is configured to, in decompressing the segment, compute the pixel value vector by forming a linear combination of the basis vectors using the plurality of expansion coefficients.